Estrogen receptor-related protein was examined on gastrectomy specime from 16 cases of advaced gastric adenocarcinoma and 7 cases of early gastric carcinoma(EGC) by using peroxidase-anti-peroxidase method on formalin-fixed paraffin-embedded sections. Positive reaction was seen in 7 out of 16 cases of advanced carcinoma and in 4 out of 8 cases of EGC(50%). Among advanced carcinoma, 3 cases of mucinous carcinoma were negative and 2 cases of signet ring cell carcinoma(SRC) showed focal positive reaction only in combined poorly differentiated(PD) area(10% of tumor cells). PD advanced carcinoma consisted of 4 cases of medullary type and 3 cases of individual cell type. Two out of 4 medullary type showed positive reaction in 20 and 80% of tumor cells and 2 out of 3 individual cell type showed positive reaction in 50 and 70% of tumor cells. Gland-forming type of advanced carcinoma consisted of 1 each case of intestinal and cardiac type and 1 mixed intestinal and cardiac type. Only 1 case of intestinal type showed positive reaction in 50% of tumor cells Among EGC, 2 cases of SRC were negative and 2 cases of PD carcinoma showed 5 and 10% positivity in PD area and 20 and 40% positivity in admixed gland-forming area. Gland-forming EGC consisted of 3 cased of intestinal type and 1 case of cardiac type. One case from each group showed positive reaction in 50 and 20% of tumor cells, respectively. In summary, positive reaction to antibody to estrogen receptor-related protein(P29) was expressed in PD(66.7%), gland-forming(50%), SRC, and mucinous type in order in both early and advanced carcinoma. The difference between age, sex, and other factors was not clear due to limitation of specimen.